The present invention relates to a technology for processing digital data and a technology for encrypting and decrypting data. The present invention also relates to, for example, a technology effective for application to the protection of data of digital contents handled by electronic equipment having a serial bus interface of an IEEE1394 (Institute of Electrical and Electronics Engineers 1394) standard, i.e., prevention of illegal copy of data.
The IEEE1394 standard is a standard of a communication interface for serially transmitting digital data such as voice, video, etc. between electronic equipment such as an AV device or apparatus, etc. through cables. In the IEEE1394 standard, data such as voice, video data, etc. which are in need of real-time transfer, make use of isochronous transfer corresponding to a synchronous transfer system, whereas asynchronous transfer corresponding to an asynchronous transfer system is used for the transfer of command data or the like for controlling between AV apparatuses.
In recent years, electronic equipment such as a tuner (i.e., IRD(Integrated Receiver Decoder)), a DTV (Digital Television), a D-VHS (Digital-VHS), an HDD (Hard Disk Drive) recorder, a DVC (Digital Video Camcorder), etc. have respectively been equipped with a serial bus interface of the IEEE1394 standard. Incidentally, the D-VHS, HDD recorder and DVC of the AV apparatuses mentioned above are of recording/reproducing apparatuses each capable of performing recording to a recording medium. Digital contents such as voice data, video data received by these, e.g., the IRD are borne or superimposed on MPEG2-TS (Moving Picture Experts Group Phase 2 Transport Stream) of an ISO/IEC (International Standardization Organization/ International Electrotechnical Commission) 13818 standard, a packet based on an IEC618883 standard, etc. and transmitted to an IEEE1394 spec cable (hereinafter called simply “1394 cable”) corresponding to a communication medium of a serial bus (hereinafter called simply “1394 bus”) of an IEEE1394 standard, followed by reception thereof with, for example, the D-VHS device, whereby the contents can be recorded in a D-VHS magnetic tape.
However, since the digital contents are not deteriorated in picture quality and sound quality or the like upon their recording even if the digital contents are repeatedly copied again and again, a technology for preventing an illegal copy in terms of protection of copyright is essential to digital contents such as motion pictures, etc. Therefore, as an illegal copy preventions technology intended for IEEE1394, 5C-DTCP (5 Company Digital Transmission Copy Protection) specs determined by a CPTWG (Copy Protection Technical Working Group) as a leading part, which is of an economic group organized by the consumer electronics industry, PC industry and Picture industry or the like, have been put into practical use at present (DTLA issue: refer to 5C Digital Transmission Copy Protection White Paper 1998.7.14).
Copy management under the 5C-DTCP specs is performed by copy management information called an EMI (Encryption Mode Indicator) contained in a packet. The EMI is made up of 2 bits and managed by any mode of {circle around (1)} “copy may be done freely” {circle around (2)} “no copy is permitted” {circle around (3)} “copy is permitted only once ” and {circle around (4)} “no further copy is permitted” according to the contents thereof. Digital content transmitting electronic equipment inserts the EMI into a packet header of the content to be transmitted and transmits it to the 1394 cable, whereas packet receiving electronic equipment makes a decision as to whether the content should be recorded, from the EMI inserted into the received packet header.
Since plural electronic equipment can be simultaneously connected onto the same bus under the IEEE1394 standard, a digital content can be transmitted from given electronic equipment to the plural electronic equipment. Thus, when, for example, the IRD is transmitting a copy-restricted content to the D-VHS recorder through the 1394 cable, content data can be intercepted by connecting, for example, an illegal device onto the same bus.
Therefore, the 5C-DTCP specs define that when data other than freely copy-permitted contents is transmitted and received through the 1394 cable, a transmitting device encrypts the content and transmits it, whereas a receiving device decrypts the received encrypted content to thereby enable the reproduction and recording of the content. An encryption/decryption system at this time is defined under the 5C-DTCP specs. Only legal or proper devices manufactured under license are capable of transmitting and receiving the copy-restricted content and encrypting and decrypting the same.
The D-VHS device will now be taken by way of example. When a once-only copyable content received via the 1394 cable is recorded, the encrypted content is transferred to the 1394 cable as described above and the D-VHS device decrypts and records it. However, the D-VHS device generally records a non-encrypted content on a D-VHS tape. At this time, however, the copy management information EMI is changed from “copy is permitted only once” to “no further copy is permitted”, and this information is also recorded on the tape together. Thus, even when the D-VHS tape having recorded the once-only copyable content thereon is reproduced and the content is transferred to other recording apparatus through the 1394 cable, copy management information EMI of the content received by other recording apparatus is indicative of “no further copy is permitted” and hence the content cannot be recorded, thus resulting in the protection of copyright of the content.
On the other hand, when the HDD recorder records the once-only copyable content received via the 1394 cable according to a system similar to the D-VHS device, since non-encrypted data is recorded in HDD, the HDD is withdrawn from the HDD recorder to thereby allow peeping of the contents of the HDD by a PC or the like and illegal copying. Therefore, the data recorded in the HDD is generally encrypted in the HDD recorder. However, no particular provision exists in this encrypting and recording technology at present. HDD-recorder manufacturers have adopted C2 encrypt recording or the like defined by 4C-Entity in which the standardization of a copyright protection system related to a recording media, for example, has been performed.
As an encryption and decryption communication semiconductor device, there has recently been developed one to which the 5C-DTCP specs are applied and which corresponds to the IEEE1394 standard. It has been posted on a home page of a semiconductor manufacturer or the like on the Internet. This type of cryption and decryption communication semiconductor device has been mounted in many AV apparatuses such as the IRD, D-VHS device, etc. each of which handles an MPEG2-TS format.
One example considered as an encryption and decryption communication semiconductor device, and a configurational example of an HDD recorder mentioned as one example of an MPEG2-TS format AV apparatus are shown in FIG. 10.
In FIG. 10, reference numeral 100 indicates an HDD recorder, and reference numeral 110 indicates an encryption and decryption communication semiconductor device. When the cryption and decryption communication semiconductor device 110 transmits the content to 1394 cables 60, it encrypts data of an MPEG2-TS format sent from an MPEG processing circuit 150 or an encryption/decryption circuit 120 such as an MPEG codec semiconductor device or the like through the use of an encryption/decryption circuit 123 via an external interface I/F (interface) 114 and effects packetize based on the IEC61883 standard on the data by virtue of a packet processing circuit 113. Thereafter, a 1394 LINK (IEEE1394 Link Layer) 111 effects processing of a LINK layer based on the IEEE1394 standard thereon and transmits it to a 1394 PHY (IEEE1394 Physical Layer) 130 used as a physical layer of the IEEE1394 standard, from which the content is transmitted to apparatuses such as an IRD, D-VHS, etc. via the 1394 cables 60 connected to the tip of the 1394 PHY 130.
On the other hand, when the HDD recorder 100 receives the content therein, the 1394 PHY 130 receives a packet sent from the corresponding 1394 cable 60 and the 1394 LINK 111 effects processing of the LINK layer thereon. Thereafter, the packet processing circuit 113 unpacketizes it and the encryption/decryption circuit 123 decrypts encrypted data. Further, the encryption/decryption circuit 123 transmits the decrypted content to the MPEG processing circuit 150 via the external I/F 114, where a process for performing reproduction, recording and the like of the content is carried out.
As another cryption and decryption communication semiconductor device mounted to an HDD recorder, there is considered one having, for example, two pairs of MPEG2-TS format external interfaces and encryption/decryption circuits, and a packet processing circuit. Alternatively, there is considered one wherein an HDD recorder is equipped with the cryption and decryption communication semiconductor device, whereby the content already recorded in HDD can be transmitted to another 1394 corresponding device while the content sent from the corresponding 1394 cable is being recorded therein.
Further, there is also considered an encryption and decryption communication semiconductor device for AV apparatuses, in which an encryption/decryption circuit is provided as one whereas an MPEG2-TS format external interface and a DV format external interface, and two packet processing circuits are provided, and which is configured so as to be capable of coping with an MPEG2-TS format and a DV format. The reason why the cryption and decryption communication semiconductor device builds one encryption/decryption circuit alone therein, is that since data of the DV format is data normally photographed privately with a DVC or the like, it is considered that there is no need to encrypt it in terms of copyright protection at the present moment.